I didn't know what a sound machine is. I looked it up.
Is that what you're looking for, a box that makes noise?
I would go to Goodwill or some used place that sells old used stuff.
Buy an old radio with a dial tuner and tune in different types of static.
See if that works. It should cost .99 cents to $2.79.
I am not being sarcastic. I realize some people like to have fans going, or nature sounds, or other types of noise when they are trying to fall asleep.
Have you tried anything yet? Have you already determined that your child wants noise?(pink or white, or whatever.)